Can fat loss be different for certain people?

Question

Is there any research that shows different people responding to certain ways/degrees of fat loss better than others.

Ie: Let’s say both people are the same weight, body fat, and level of fitness, and in a calorie deficit of 400 calories from maintenance. They have accurate food tracking, and workout logs, and yet person A shows more fat loss than person B over a certain span of time.

However, if the amount of calories were different, say 1000 cal deficit from maintenance, person b shows increased fat loss over person A.

Answer 1

If two people had a magic machine that was capable of telling them exactly what the metabolism was at any given day, and generate a meals that would give them exactly the same deficit consistently every day, then they would lose the same weight at roughly the same rate.

However, their body's response to the weight loss could be different. Person A may perform their daily activities with less energy than Person B. Person A may feel more sluggish and lethargic then Person B, which in turn causes them to be less active. Person A may feel hungrier which demotivates them to do things they normally would do under normal circumstances, which in turn causes them to be less active. These things can cause Person A's metabolism to drop. This magic machine would then have to adjust Person A's calories more often than Person B.

We know this happens because there's a class of nutrition study called Metabolic Ward studies which try to emulate this as close as possible. People are housed and fed extremely strict diets while their metabolism is monitored. These studies are often extremely short and small considering the difficulty in convincing people to live like this for an extended period of time. Though whenever these studies are conducted, people's weight drops predictably but not exactly because their metabolism changes at different rates.

Answer 2

Some people have faster metabolisms, or more muscle mass making weight loss easier but that's just because those things make a calorie deficit easier to do. Assuming, as stated in you example, both people have the same deficit, and therefore the same diet and training program, the fat loss will be very similar. Its just a law of thermodynamics, if you consume 400cal less than your TDEE, your body will have to burn 400cal worth of fat. When looking at the scales, there may be a difference though. Adipose tissue (fat) is generally made up of 1-2% proteins, ~29% water, and ~69% actual fat cells. Those figures can vary a small amount just based on genetics and a lager amount based on fitness level and body-fat%. So, assuming your examples subjects have similar height, weight, fitness level and BF%, the weight loss will be pretty close.